cannot declare an array in c with a variable value

Question

I am trying to create a program to generate magic square by a given value of n in C language. here is the code

#include<stdio.h> 
#include<string.h> 

// A function to generate odd sized magic squares 
void generateSquare(int n) 
{ 
    int magicSquare[n][n]; 

    // set all slots as 0 
    memset(magicSquare, 0, sizeof(magicSquare)); 

    // Initialize position for 1 
    int i = n/2; 
    int j = n-1; 

    // One by one put all values in magic square 
    for (int num=1; num <= n*n; ) 
    { 
        if (i==-1 && j==n) //3rd condition 
        { 
            j = n-2; 
            i = 0; 
        } 
        else
        { 
            // 1st condition helper if next number  
            // goes to out of square's right side 
            if (j == n) 
                j = 0; 

            // 1st condition helper if next number  
            // is goes to out of square's upper side 
            if (i < 0) 
                i=n-1; 
        } 
        if (magicSquare[i][j]) //2nd condition 
        { 
            j -= 2; 
            i++; 
            continue; 
        } 
        else
            magicSquare[i][j] = num++; //set number 

        j++; i--; //1st condition 
    } 

    // Print magic square 
    printf("The Magic Square for n=%d:\nSum of "
       "each row or column %d:\n\n",  n, n*(n*n+1)/2); 
    for (i=0; i<n; i++) 
    { 
        for (j=0; j<n; j++) 
            printf("%3d ", magicSquare[i][j]); 
        printf("\n"); 
    } 
} 

// Driver program to test above function 
int main() 
{ 
    int n = 7; // Works only when n is odd 
    generateSquare (n); 
    return 0; 
}

while compiling the program in turbo c compiler i get the following errors

line 7 constant expression required

line 13 declaration not allowed here

line 14 declaration not allowed here

undefined symbol num

the program works well if i run it as a c++ file but it shows errors as a c program

You need a C compiler that supports C99. Turbo C is way too old. — Paul R
– Paul R, Commented Nov 13, 2018 at 16:24
VLAs were introduced in C99. Your compiler is probably too old to support that language standard. — Swordfish
– Swordfish, Commented Nov 13, 2018 at 16:24

Sahil Singh · Accepted Answer · 2018-11-13 17:57:38Z

1

You are probably using TurboC.

TurboC uses an outdated compiler of C language. It supports Borland Compiler . It was preferable when windows Xp was in trend. It has now become obsolete.

Use latest gcc or g++ instead.

You may shift to Ubuntu or Mac

or can try CodeBlocks for Windows.

answered Nov 13, 2018 at 17:57

Sahil Singh

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